The control culture medium was use and the carbon sources (sucrose) and the inducer of phytase production (sodium phytate) were further optimized in the synthetic medium by RSM and by using central composite design (CCD). One milliliter of yeast preinoculum was used in all the experiments. In this manner, we sought to determine the optimal concentrations of these compounds and to study their interactions. Urea was fixed as nitrogen source at concentration of 0.15% (w/v). The concentrations of these two variables (sodium phytate concentration (A) and sucrose concentration (B)) were optimized using the CCD plan and Statistica software (version 7.0). Each variable in the design was studied at five different levels (Table 1). A 22 factorial design, with four axial points and three replicates at the center point and a total of 11 experiments were employed (Table 2). The average maximum phytase activity in S. cerevisiae cultured in sodium phytate substrate was measured after 36h of fermentation. The behavior of the system can be explained by the following quadratic equation